A wide variety of applications exist for miniature or micro-scale pumping systems. Such applications typically require pumping of small volumes of liquid or gases on a periodic basis. One example of an application for a miniature or micro-scale pump would be in controlled drug delivery, as delivery of insulin to a diabetic. A miniature pump including a supply of insulin could be carried either on the person, or theoretically implanted within the patient, for controlled delivery of insulin at appropriate times throughout the day. Miniature pumps could also be adapted for use in micro-chemical analysis and monitoring in a wide variety of fields and for micro-synthesis. In the environmental field, for example, a given quantity of chemicals could be periodically tested by pumping out a small sample by means of a miniature pump and performing the necessary analysis on that small sample perhaps with the required analyzing chemicals being similarly pumped. A wide variety of other applications for miniature pumps could also be envisioned.
Miniature pumps to meet these applications have been under extensive development for about the last decade. Most of these miniature pumping devices are based on either thermal, electrohydrodynamic, or piezoelectric actuation phenomenon. In the case of thermal or electrohydrodynamic systems, miniaturization can be achieved, but the resulting pumps have very low cycle times based on inherent limits in the actuation processes. As a result, the ability for such pumps to be incorporated into efficient pumping schemes is limited. The pumps based on the piezoelectric effect, on the other hand, have the required low cycle times. These devices, however, require very high voltages (on the order of 100 volts) for operation. The need for such a sizeable power supply can be quite limiting to implementation of such a pumping system, and may prevent use of such a pumping system depending upon the application. Thus, while miniature or micro-scale pumps are in existence, they have practical limitations which prevent their efficient implementation.